1. Field of the Invention
The present invention pertains to the art of immobilizing bioactive materials and particularly relates to an improved microsponge for use in motive bioreactor systems. The present invention also relates to the art of culturing microorganisms and cells, hereinafter referred to collectively as organisms, and particularly relates to the culturing of organisms immobilized on and/or in microsponges in motive reactor systems as submerged suspensions.
2. Description of the Prior Art
Various arrangements for immobilizing bioactive materials are known. Solid supports have long been used for immobilizing microorganisms in the treatment of waste water and related fermentation processes. More recently, solid microcarriers have been used to obtain high cell densities in the culture of attachment-dependent cells. For example, microporous polymeric supports fabricated for example from dextran have been used for cultivating cells. Such supports can be obtained commercially from Pharmacia Fine Chemicals under the brand name Cytodex.RTM.. Such solid bio-supports, however, are not suitable for motive reactor systems such as vigorously stirred tanks and fluidized beds since substantially all of the cells are adherent to the surface of said supports and thus are exposed to impact stress and trauma during operation.
Porous inorganic microcarriers also are known and such supports potentially provide protection for the cells in motive applications since the cells populate the interior of the microcarriers. Unfortunately, inorganic microcarriers cannot be made with the proper combination of permeability and specific gravity to function well in all motive applications. For example, the porous fritted glass or cordierite supports described in Messing et al. U.S. Pat. No. 4,153,510 would typically exhibit specific gravities in aqueous suspension of less than about 1.3 if their void fractions are greater than about 80% (Note that void fractions for the Messing supports are not disclosed). Quite understandably, these supports are not suitable for all motive rector systems where a higher specific gravity generally is needed to ensure high relative velocities for maximum rates of mass transfer. Consequently, these supports have generally been relegated for use in packed bed applications.
An object of the present invention is to provide a microsponge containing immobilized bioactive materials suitable for use in motive reactor systems.
An object of the present invention is to provide a microsponge suitable for immobilizing a large variety of microorganisms characterized by wide variations in size and their degree of attachment to solid supports.
A further object of the present invention is to provide a microsponge suitable for motive reaction systems which permits the continued growth and reproduction of immobilized organisms.
It also is An object of the present invention is to provide a microsponge suitable for motive reactor systems which is conducive to maximizing the metabolic activity of immobilized organisms.
Yet Another object of the present invention is to provide a method for continuously culturing organisms of high concentrations.
Still Another object of the present invention is to provide a microsponge suitable for motive reactor systems which permits the culturing of organisms at high concentrations while accommodating either maximum growth rate or maximum metabolic activity.
These and other objects of this invention will become apparent from a consideration of the specification and appended claims.